Abstract:

It is therefore an object of the present invention to provide a forming
method for a resist pattern to reduce a resist residue in forming the
resist pattern on a step whose gradient angle is equal to 90 degrees or
more.
A forming method for a resist pattern to reduce a resist residue on a step
is provided, the method comprising: forming resist film with coating
resist containing photo-acid-generator on a step formed on a substrate,
where gradient angle of the step is equal to 90 degrees or more, exposing
said resist film and generating acid from said photo-acid-generator.

Claims:

1. A forming method of a resist pattern to reduce a resist residue on a
step, the method comprising steps of:forming a resist film with coating
resist containing photo-acid-generator on a step formed on a substrate,
where gradient angle of the step is equal to 90 degrees or more;
andexposing said resist film and generating acid from said
photo-acid-generator.

2. The forming method as claimed in claim 1, wherein a concentration of
said photo-acid-generator is less than 1% by weight.

3. The forming method as claimed in claim 1, wherein said
photo-acid-generator is either Triphenylsulfoniumhexafluoroantimonate
photo-acid-generator, Triphenylsulfonium type photo-acid-generator, or
Bisiodonium type photo-acid-generator.

4. The forming method as claimed in claim 1, wherein baking of said resist
film is preformed at from 60.degree. C. to 70.degree. C. after forming
said resist film and before said exposure.

5. The forming method as claimed in claim 1, wherein baking of said resist
film is preformed at 60.degree. C. after forming said resist film and
before said exposure.

6. The forming method as claimed in claim 4, wherein said exposure of the
resist film is an extend exposure.

7. A manufacturing method of a thin-film magnetic head forming a side
shield with a resist pattern, the method comprising steps of:forming a
resist film with coating resist containing photo-acid-generator on a main
magnetic pole layer formed on a substrate, where gradient angle of the
main magnetic pole layer is equal to 90 degrees or more;exposing a
portion where the main magnetic pole layer is formed along height
direction and generating acid from said photo-acid-generator; andforming
the resist pattern to reduce a resist residue on the main magnetic pole
layer.

8. The manufacturing method as claimed in claim 7, wherein said side
shield is formed by forming a convex portion of magnetic metal material
covering said main magnetic pole layer, eliminating said resist pattern,
and then polishing said convex portion.

9. The manufacturing method as claimed in claim 7, wherein a concentration
of said photo-acid-generator is less than 1% by weight.

10. The manufacturing method as claimed in claim 7, wherein said
photo-acid-generator is either Triphenylsulfoniumhexafluoroantimonate
photo-acid-generator, Triphenylsulfonium type photo-acid-generator, or
Bisiodonium type photo-acid-generator.

11. The manufacturing method as claimed in claim 7, wherein baking of said
resist film is preformed at from 60.degree. C. to 70.degree. C. after
forming said resist film and before said exposure.

12. The manufacturing method as claimed in claim 7, wherein baking of said
resist film is preformed at 60.degree. C. after forming said resist film
and before said exposure.

13. The manufacturing method as claimed in claim 11, wherein said exposure
of the resist film is an extend exposure.

Description:

BACKGROUND OF THE INVENTION

[0001]1. Field of the Invention

[0002]The present invention relates to a forming method of a resist
pattern with chemically-amplified resist and a manufacturing method of a
thin-film magnetic head with the resist pattern formed with this method.

[0005]In this case, the photo resist pattern could be formed on steps
formed on a substrate. Especially, in an integrated process, for example,
a perpendicular magnetic head, there is a case to have to form the resist
pattern so as to cover a magnetic pole having the steps whose gradient
angle is equal to 90 degrees or more. In case of forming a positive type
photo resist pattern, the steps make shade portions, then sufficient
exposure is not performed in the shade portions. In forming the positive
type photo resist pattern, the resist pattern is formed by eliminating
the exposed portion with development so that the unexposed portion is
residual without eliminating with the development. If the portion which
should be exposed is not exposed, a resist residue could occur at this
portion. The resist residue causes a problem that this portion does not
apply plating well in latter process.

[0006]For example, we consider forming the resist pattern on the step
formed on the substrate as FIG. 1a. In the step, gradient angle θ
is 90 degrees or more. Here, the angle θ is a supplementary angle
of an angle φ between a wall surface 10 and a surface 11 of a layer
containing the step. The resist pattern is formed by coating the resist
on the step, exposing the resist via a reticle, etc., and then developing
the resist. In the case of forming the resist pattern 12 as FIG. 1b, it
can occur a ledge of the resist (a resist residue 13) at the portion
among the wall surface 10, the surface 11 of the layer containing the
step, and the resist pattern 12. In FIG. 1b, a darker-shaded area is the
resist residue 13. Since the gradient angle θ is equal to 90
degrees or more, exposing light is shielded by the step. For this reason,
unexposed portion is made. In the case of plating resist pattern formed
above, the tracing of the portion of resist residue 13 causes a problem
that a desired plating is not formed.

BRIEF SUMMARY OF THE INVENTION

[0007]It is therefore an object of the present invention to provide a
forming method for a resist pattern to reduce a resist residue in forming
the resist pattern on a step whose gradient angle is equal to 90 degrees
or more. Further, it is another object of the present invention to
provide a manufacturing method of a thin-film magnetic head with the
resist pattern formed with this method.

[0008]According to the present invention, a forming method for a resist
pattern to reduce a resist residue on a step is provided, the method
comprising steps of: forming a resist film with coating resist containing
photo-acid-generator on a step formed on a substrate, where gradient
angle of the step is equal to 90 degrees or more, exposing said resist
film and generating acid from said photo-acid-generator.

[0009]It is preferable that a concentration of said photo-acid-generator
is less than 1% by weight.

[0010]It is preferable that said photo-acid-generator is either
Triphenylsulfoniumhexafluoroantimonate photo-acid-generator,
Triphenylsulfonium type photo-acid-generator, or Bisiodonium type
photo-acid-generator.

[0011]It is preferable that baking of said resist film is preformed at
from 60° C. to 70° C. after forming said resist film and
before said exposure. Further, It is more preferable that baking of said
resist film is preformed at 60° C. after forming said resist film
and before said exposure.

[0012]When temperature of the pre-bake is lower, residual solvent in the
resist remains much. Since diffusion of the photo-acid-generator becomes
large, this makes the photo-acid-generator reach unexposed portion or
hardly exposed portion. As a result, the pre-bake at 70° C. makes
a width of the resist residue decrease less than a half width of
120° C. Further, the pre-bake at 60° C. makes a width of
the resist residue decrease less than a quarter width of 120° C.

[0013]It is preferable that said exposure of the resist film is an extend
exposure.

[0014]When temperature of the pre-bake is lower, the diffusion of the
photo-acid-generator becomes large, and then resolution of the resist
pattern degrades. Therefore, a problem of the degradation of the
resolution can be resolved with the extend exposure instead of normal
exposure.

[0015]According to the present invention, a manufacturing method of a
thin-film magnetic head forming a side shield with a resist pattern; the
method comprising steps of: forming a resist film with coating resist
containing photo-acid-generator on a main magnetic pole layer formed on a
substrate, where gradient angle of the main magnetic pole layer is equal
to 90 degrees or more, exposing a portion where the main magnetic pole
layer is formed along height direction and generating acid from said
photo-acid-generator, forming the resist pattern to reduce a resist
residue on the main magnetic pole layer.

[0016]It is preferable that said side shield is formed by forming a convex
portion of magnetic metal material covering said main magnetic pole
layer, eliminating said resist pattern, and then polishing said convex
portion.

[0017]It is preferable that a concentration of said photo-acid-generator
is less than 1% by weight.

[0018]It is preferable that said photo-acid-generator is either
Triphenylsulfoniumhexafluoroantimonate photo-acid-generator,
Triphenylsulfonium type photo-acid-generator, or Bisiodonium type
photo-acid-generator.

[0019]It is preferable that baking of said resist film is preformed at
from 60° C. to 70° C. after forming said resist film and
before said exposure. Further, It is more preferable that baking of said
resist film is preformed at 60° C. after forming said resist film
and before said exposure. Further, it is preferable that said exposure of
the resist film is an extend exposure.

[0020]The side shield formed by the forming process is formed only in
front of height direction of the main magnetic pole layer because a
resist wall is positioned in the back to height direction of the main
magnetic pole layer. Also, in the resist wall, the resist residue does
not influence the forming of the side shield because the resist residue
is reduced.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0021]FIGS. 1a and 1b are schematic diagrams showing occurrence of a
resist residue when a resist pattern is formed on a step, whose gradient
angle is 90 degrees or more, formed on substrate, by a conventional
forming method of the resist pattern;

[0022]FIGS. 2a to 2f are perspective views explaining an embodiment of a
forming method of a resist pattern according to the present invention;

[0023]FIG. 2g is a flowchart showing an embodiment of a forming method of
a resist pattern according to the present invention;

[0027]FIG. 4 is a schematic diagram of a wafer showing one embodiment of
the extend exposure;

[0028]FIG. 5 is a schematic diagram of a resist pattern formed on a step
on a substrate, where gradient angle of the step is equal to 90 degrees
or more, with pre-baked at 120° C. which is an ordinary range with
a chemically-amplified resist;

[0029]FIG. 6 is a graph showing an experimental result of Table 1;

[0030]FIG. 7 is a graph showing an experimental result of Table 3; and

[0031]FIGS. 8a1 to 8f2 are schematic diagrams explaining succession of
flows of the side shield forming process.

DETAILED DESCRIPTION OF THE INVENTION

[0032]FIGS. 2a to 2f are perspective views explaining an embodiment of a
forming method of a resist pattern according to the present invention.
Also, FIG. 2g is a flowchart showing an embodiment of a forming method of
a resist pattern according to the present invention.

[0033]FIG. 2a shows a layer 21 containing a step formed on a substrate 20
according to the present embodiment. As the substrate 20, in the case of
a thin film device such as a thin-film magnetic head, for example, AlTic
substrate is used. The step has a gradient angle which is equal to 90
degrees or more. Here, the angle θ is a supplementary angle of an
angle φ between a step wall surface 22 and a surface 23 of a layer
containing the step.

[0034]First, as shown in FIG. 2b, a resist film 24 whose thickness is
approximately 1.0-2.0 μm (micro meter) is formed on the layer 21
containing the step with coating a chemically-amplified positive type
resist containing photo-acid-generator whose concentration is less than
1% by weight(step S1(FIG. 2g)).

[0035]As a high sensitive resist, a chemically-amplified resist is known,
so the present invention uses the chemically-amplified resist. A
conventional resist essentially utilizes photoreaction caused by exposure
of light or electron beam, whereas the chemically-amplified resist
contains the photo-acid-generator in the resist component and utilizes
generated acid which serves as a catalyst. The chemically-amplified
resist has a feature that significant sensitive increases are
accomplished by utilizing catalytic reaction.

[0038]Next, as shown in FIG. 2c, a baking before an exposure (pre-baking)
is performed at temperature of 60° C.-120° C. for 1.5-4
minutes (step S2 (FIG. 2g)). After forming the resist film 24, the
pre-baking is preformed to evaporate solvent in the resist.

[0039]When temperature of the pre-bake is lower, the diffusion of the
photo-acid-generator becomes large, and then resolution of the resist
pattern degrades. For this reason, typically, temperature of the pre-bake
is high temperature such as 80° C.-120° C., preferably
100° C. or more.

[0040]When residual solvent in the resist remains much, it is found that
diffusion distance of the photo-acid-generator becomes large. Since the
pre-bake has the function eliminating this solvent, with the temperature
of the pre-bake being lower than usual, residual solvent is much so that
the diffusion distance of the photo-acid-generator becomes large. This
makes photo-acid-generator reach unexposed portion or hardly exposed
portion. As a result, the resist residue decrease.

[0041]Next, as shown in FIG. 2d, an exposure is performed (step S3 (FIG.
2g)). The exposure irradiates the resist film 24 by Deep UV light 25 such
as excimer laser whose wavelength is 248 nm with a predetermined pattern
via a reticle 26. This exposure generates a few acid 27 at the exposed
portion.

[0042]Thereafter, a baking after the exposure (post bake, PEB, Post
Exposure Bake) is performed at temperature of approximately 60°
C.-100° C. for 1.5-4 minutes (step S4 (FIG. 2g)). Since the post
bake provides heat energy, the acid 27 generated by the exposure is
diffused so that solubility toward alkaline developer becomes large at
the exposed portion.

[0043]Finally, as shown in FIG. 2f, a development forms resist pattern 28
by eliminating the portion where the acid is generate, with the alkaline
developer of predetermined concentration.

[0044]As above explained, this method uses the chemically-amplified resist
in order to reduce a resist residue in forming the resist pattern on a
step whose gradient angle is equal to 90 degrees or more. In other words,
by using chemical method not optical method, this method make the acid
reach unexposed portion or hardly exposed portion so that the resist
residue is reduced.

[0045]Further, this method uses an extend exposure instead of a usual
exposure at the exposure in FIG. 2d to resolve the problem that
resolution of the resist pattern degrades due to the lower pre-bake
temperature than usual.

[0046]The extend exposure is the exposure method that wafer divides shots
then an exposure amount is adjusted to each shot. First, the extend
exposure measures resist width at each shot of some wafer and classifies
the shot into a plurality of groups according to deviation from the mean
value of the resist width. Since the resist width of each shot is the
same in any wafer, it is sufficient to measure the resist width in one
wafer. Next, the extend exposure defines the most suitable exposure
amount at each classification according to the measured resist width. The
extend exposure is the method that each shot is exposed by the exposure
amount due to the classification.

[0047]FIG. 4 is a schematic diagram of wafer showing one embodiment of the
extend exposure. In this figure, there are sixteen shots 41 in the wafer
40. Measuring the resist width to each shot, the shots are classified
into A, B, and C by the resist width. For example, the class A has the
resist width more than the mean value+the standard deviation, the class B
has the resist width less or equal to the mean value+the standard
deviation and more or equal to the mean value-the standard deviation, and
the class C has the resist width less than the mean value-the standard
deviation. The suitable exposure amounts EA, EB, EC are defined to each
class A, B, C. When exposing the wafer of each shot, the shot of class A
is exposed by the exposure amount EA, the shot of class B is exposed by
the exposure amount EB, and the shot of class C is exposed by the
exposure amount EC. In this figure, the shots are only sixteen, but there
might be more shots for real wafer. Further, in this example, the
classifications of the shots are three, but they might be other than
three.

[0048]As explained above, since the extend exposure gives the suitable
exposure amount to each shot, the extend exposure resolves the problem
that resolution of the resist pattern degrades.

[0049]Further, as above mentioned, the baking after the exposure (PEB) is
performed in the chemically-amplified resist. The PEB is performed to
diffuse evenly the acid generated by the exposure. For this reason,
adjustment of the PEB temperature as well as the pre-bake temperature can
make acid reach unexposed portion or hardly exposed portion. However, the
adjustment of the PEB temperature doesn't change the width of the resist
residue.

[0050]Further, although the present embodiment is the method to form the
resist pattern on the layer including the steps formed on the substrate,
the present invention is applicable to form the resist pattern on the
substrate including the steps.

[0051]Below, using practical examples and a comparative example, the
effect of the forming method of resist pattern according to the present
invention is explained.

COMPARATIVE EXAMPLE

[0052]FIG. 5 is a schematic diagram of a resist pattern 52 formed on a
step on a substrate, where gradient angle of the step is equal to 90
degrees or more, with pre-baked at 120° C. which is an ordinary
range with a chemically-amplified resist. As a result, a resist residue
53 is generated at the portion among a wall surface 50, a surface 51 of
the layer containing the step, and a resist pattern 52. In FIG. 5, a dark
portion enclosed in the dotted line is the resist residue 53. A resist
residue width WR is defined as the width from an edge face 54 of the
resist pattern to a portion where the resist residue 53 vanishes. In FIG.
5, the width between the dotted lines along an x-axis corresponds the
resist residue width WR. Moreover, as shown in latter experimental
result, this measured value was 203 nm (nanometer).

[0053]As above explained, using the chemically-amplified resist instead of
the photo resist with the pre-bake at 120° C. which is an ordinary
range, the resist residue could not be sufficiently reduced, which is
generated when the resist pattern was formed on the step on the
substrate, where gradient angle of the step is equal to 90 degrees or
more.

PRACTICAL EXAMPLE 1

[0054]Table 1 shows an experimental result about a relationship between
the pre-bake temperature and the resist residue width WR when the resist
pattern is formed on the step formed on the substrate, where the gradient
angle of the step is 90 degree or more, using chemically-amplified resist
and lowering the temperature of the pre-bake. Also, FIG. 6 is a graph
showing an experimental result of Table 1.

[0055]According to the Table 1, it is found that the resist residue width
WR reduces with lower and lower the pre-bake temperature. For example,
when the pre-bake temperature is 60° C., the resist residue width
WR is 49 nm. In this way, the low pre-bake temperature makes the resist
residue width WR reduce sufficiently.

[0056]Further, when a plating applies to the resist pattern, the resist
residue width WR should be equal to or lower than 100 nm to form a
desired plating. Therefore, the pre-bake temperature should be equal to
or lower than 70° C. according to FIG. 6.

[0057]In this way, the pre-bake temperature 70° C. makes the resist
residue width WR reduce less than half that of the pre-bake temperature
120° C. Further, the pre-bake temperature 60° C. makes the
resist residue width WR reduce less than quarter that of the pre-bake
temperature 120° C.

[0059]However, the diffusion of the photo-acid-generator has a side-effect
that resolution of the resist pattern degrades. Therefore, in order to
confirm the degradation of the resolution of the resist pattern due to
the low pre-bake temperature, the degradation of the resolution is
measured by the experiment to form the resist pattern with the
chemically-amplified resist, the pre-bake at 120° C., 80°
C., and 60° C., and the exposure. The result of the degradation of
the resolution of the resist pattern due to the low pre-bake temperature
is shown below.

[0060]Table 2 shows an experimental result about a relationship between
the pre-bake temperature and three times a standard deviation 3σ of
the resist residue width WR when the resist pattern is formed with
chemically-amplified resist and the low temperature of the pre-bake. The
experiment obtained the standard deviation σ of the measured values
with forming a plurality of the resist patterns whose width is 3.0 μm
in the wafer, selecting 40 formed resist patterns, and measuring the
resist width of the selected resist patterns.

[0061]According to this experimental result, it is found that the 3σ
of the resist width increases with lower and lower the pre-bake
temperature. For example, when the pre-bake temperature is 60° C.,
the 3σ of the resist width degenerates more than one and half times
that of the pre-bake temperature 120° C. Also, when the pre-bake
temperature is 80° C, the 3σ of the resist width degenerates
more than 1.3 times that of the pre-bake temperature 120° C. The
increase of the 3σ of the resist width can occur the case that the
resist pattern does not maintain a good shape and size.

PRACTICAL EXAMPLE 2

[0062]Table 3 shows an experimental result about the 3σ of the
resist width when the resist pattern is formed with chemically-amplified
resist, pre-bake at 60° C, and the extend exposure, for
comparison, and shows an experimental result about a relationship between
the pre-bake temperature and the 3σ of the resist width when the
resist pattern is formed with chemically-amplified resist and no extend
exposure. FIG. 7 is a graph showing an experimental result of Table 3.
Here, the result not to perform the extend exposure is the same as the
Table 2. As well as not performing the extend exposure, the experiment
obtained the standard deviation σ of the measured values with
forming a plurality of the resist patterns whose width is 3.0 μm in
the wafer, selecting 40 formed resist patterns, and measuring the resist
width of the selected resist patterns.

[0063]According to the Table 3, when the extend exposure is performed, the
3σ of the resist width becomes 0.041 μm at the pre-bake
temperature 60° C. This substantially reduces from the 3σ of
the resist width 0.075 μm at the pre-bake temperature 60° C.
when the normal exposure is performed. Further, this value of the extend
exposure is lower than the 3σ of the resist width 0.048 μm at
the pre-bake temperature 120° C. when the normal exposure is
performed. This shows that the sufficient resolution of the resist
pattern can be obtained by using the extend exposure even if the pre-bake
temperature is 60° C.

[0064]As mentioned above, the problem that the degradation of the
resolution occurs at the low pre-bake temperature is resolved by using
the extend exposure instead of the normal exposure.

(Side Shield Forming Process)

[0065]Next, the side shield forming process of a write head element, which
uses the resist pattern formed by the present embodiment, in a thin-film
magnetic head is explained.

[0066]The side shield is set in a neighborhood of side portion at a tip of
main magnetic pole layer along a track width direction. The side shield
absorbs noise magnetic field generated from a side track. For this
reason, the side shield prevents already recorded information on same
track from reversing.

[0067]FIGS. 8a1 to 8f2 are schematic diagrams explaining succession of
flows of the side shield forming process. In these figures, FIGS. 8a1,
8b1, 8c1, 8d, 8e, and 8f1 show cross-section drawings viewed from an ABS
(air bearing surface) and FIGS. 8a2, 8b2, 8c2, and 8f2 show plane
drawings viewed from a positive z-axis.

[0068]As shown in FIG. 8a1, a main magnetic pole layer 81 is formed on a
substrate made of conductive material such as AlTiC
(Al2O3--TiC). The main magnetic pole layer 81 is a magnetic
path to guide and converge magnetic flux, which is generated with write
current applied to a write coil layer (not shown), to a perpendicular
magnetic recording layer of the magnetic disk to be written thereon. The
main magnetic pole layer 81 can form of metal magnetic material or a
multilayer of the metal magnetic material such as, for example, NiFe,
CoFe, NiFeCo, FeAlSi, FeN, FeZrN, FeTaN, CoZrNb, and CoZrTa with a
thickness of approximately 0.5-3 μm by using a frame plating. As shown
in FIG. 8a1, the main magnetic pole layer 81 is formed as shape having
the step whose gradient angle is equal to 90 degrees or more.

[0069]The main magnetic pole layer 81 is covered with a insulation layer
82. The insulation layer 82 is formed of, for example, insulation
material such as Al2O3 or SiO2 with filmed by using such
as sputtering. If need, an upper surface is planarized by using such as a
chemical mechanical polishing (CMP).

[0070]After forming the main magnetic pole layer 81, as shown in FIGS. 8b1
and 8b2, a positive type photo resist containing the photo-acid-generator
is coated on the main magnetic pole layer 81. As the resist material, the
resist material whose major component is PGMEA resist material is used.
As the photo-acid-generator, Triphenylsulfonium type
photo-acid-generator, Triphenylsulfoniumhexafluoroantimonate
photo-acid-generator, or Bisiodonium type photo-acid-generator is used.
As shown in FIGS. 8c1 and 8c2, using the forming method of the resist
pattern according to the practical example 1 or the practical example 2
of the present embodiment, a resist pattern 83 is formed, which has a
resist wall positioned in the back to height direction.

[0071]Next, as shown in FIG. 8d, as covering the main magnetic pole layer
81, a convex portion 84 is formed of metal magnetic material or a
multilayer of the metal magnetic material such as, for example, NiFe,
CoFe, NiFeCo, FeAlSi, FeN, FeZrN, FeTaN, CoZrNb, and CoZrTa with a
thickness of approximately 0.5-3 μm by using such as the sputtering or
the frame plating.

[0072]Next, as shown in FIG. 8e, with exfoliating the resist pattern 83,
an Al2O3 layer 85 is formed, for example, by using the
sputtering.

[0073]Finally, as shown in FIG. 8f1 and 8f2, by polishing the convex
portion 84 and the Al2O3 layer 85 with such as the CMP parallel
to the height direction and the track width direction until the main
magnetic pole layer 81 exposes, their surfaces are planarized. This forms
the side shields 86 at right and left of the main magnetic pole layer 81
to track width direction.

[0074]As explained above, the side shield 86 formed by the forming process
is formed at only in front of the height direction of the main magnetic
pole layer 81 because a resist wall is positioned in the back to the
height direction of the main magnetic pole layer 81. Also, in the resist
wall, the resist residue does not influence the forming of the side
shield 86 because the resist residue width reduces.

[0075]All the foregoing embodiments are by way of example of the present
invention only and not intended to be limiting, and many widely different
alternations and modifications of the present invention may be
constructed without departing from the spirit and scope of the present
invention. Accordingly, the present invention is limited only as defined
in the following claims and equivalents thereto.